CHOKE AND DAGGER: Saxa (Ellen Hollman), who’s loyal to Spartacus and his cause, takes out an enemy. Photo: A Starz Original Series

Subtle it’s not.

The opening shot of tonight’s “Spartacus” season premiere features a skull, bashed open on a battlefield, with exposed brain matter, followed by a (dead) woman’s naked breast.

That pretty much sets the cartoonishly violent tone of “Spartacus” that has made it a fan favorite heading into its fourth and final season.

Within the first five minutes, we’re treated to what plays like a 14-year-old boy’s ultimate video game fantasy — soft porn and slow-motion blood spatters and swords plunged into all parts of the body (including mouths, which weirdly seem to be a particular favorite method of Roman dispatch — who knew?).

And, while soldiers loyal both to rebel slave Spartacus (Liam McIntyre) and his enemies casually drop enough f-bombs to make David Mamet blush, we’re also treated to several decapitations — including what has to be TV’s first-ever double-decapitation, done in one fell swoop and in slow-motion, natch.

(I can just hear Maxwell Smart, if he were living in ancient Roman times as, let’s say, Maximus Smartus, on witnessing the double-decapitation: “Missed it by that much.”)

Oh yeah, there’s also a plot here, as the perpetually angry, sullen Spartacus plots his never-ending battle against Rome. It’s been a few months since the death of Gaius Claudius Glaber, and Spartacus — joined by generals Crixus (Manu Bennett), Gannicus (Dustin Clare) and Agron (Dan Feuerriegel) — is intent on bringing down the entire Republic, one slashed belly/slit throat at a time.

Meanwhile, a new character, wealthy Roman businessman Marcus Crassus (Simon Merrell) — who’s been told by the Roman Senate to destroy Spartacus and quell the rebel uprising — trains for the ultimate showdown.

Or something like that.

It’s all a muddled mess of computer-generated battlefield scenes, gratuitous bare-breast-and-buttock shots (men and women — there’s no favoritism here) and “Crouching Tiger Hidden Dragon”-type photography (someone who leaps into the air is frozen, midframe, before landing with badass intent).

Upcoming episodes will introduce Julius Caesar (yes, that Julius Caesar), but this is the kind of series where acting chops don’t count for much — and one’s value is measured more by how he or she can rock a loincloth.

To quote one of the Romans from tonight’s opener, “Confounds thef- – – ing senses!”